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Hjortebjerg R, Flyvbjerg A, Frystyk J. Insulin growth factor binding proteins as therapeutic targets in type 2 diabetes. Expert Opin Ther Targets 2013; 18:209-24. [PMID: 24261835 DOI: 10.1517/14728222.2014.858698] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
INTRODUCTION The signaling pathways of the insulin-like growth factors (IGFs) have been implicated in the aetiology of type 2 diabetes (T2D) and a number of therapeutic modalities aiming at the IGF-axis have been considered. Administration of IGF-I has been reported to improve insulin sensitivity in healthy subjects and patients with T2D. In recent years, the IGF binding proteins (IGFBPs) have also been associated with metabolic disorders, prompting the idea that IGFBPs play important roles in the pathogenesis of T2D. Thus, by virtue of their role in the regulation of IGF effects, the IGFBPs have emerged as potential biomarkers and therapeutic targets in metabolic syndromes and T2D. AREAS COVERED The article provides an overview on recent findings in clinical and experimental IGFBP-research and addresses the studies that have investigated the potentials of the IGFBPs as therapeutic targets in T2D. EXPERT OPINION There is plenty of therapeutic promise within the IGF system, but further understanding of the IGFs in T2D is necessary to avoid off-target effects. Strong evidence supports the use of IGFBPs as therapeutic targets in the treatment of T2D, and it is not difficult to foresee the use of IGFBPs as part of a combination therapy alongside other anti-diabetic drugs.
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Affiliation(s)
- Rikke Hjortebjerg
- Aarhus University, Department of Clinical Medicine, Medical Research Laboratory, Faculty of Health , DK-8000 Aarhus C , Denmark
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Gude MF, Frystyk J, Flyvbjerg A, Bruun JM, Richelsen B, Pedersen SB. The production and regulation of IGF and IGFBPs in human adipose tissue cultures. Growth Horm IGF Res 2012; 22:200-205. [PMID: 23079385 DOI: 10.1016/j.ghir.2012.09.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 09/26/2012] [Accepted: 09/27/2012] [Indexed: 01/13/2023]
Abstract
BACKGROUND Adipocytes express and secrete IGFs and IGFBPs; proteins with important effects on adipocyte homeostasis. However, the factors that control adipocyte generation of IGFs and IGFBPs are not clarified. AIM To identify regulators of the synthesis of IGFs and IGFBs in adipose tissue. METHODS Subcutaneous adipose tissue fragments (500 mg) from 7 healthy lean women were incubated for 48 h following addition of GH (50 μg/l), dexamethasone (DXM, 20 nM), insulin (100 nM), interleukin (IL)-1β (50 ng/l), IL-6 (50 ng/l) and tumor-necrosis factor (TNF)-α (10 ng/l). Outcome parameters included tissue mRNA and culture media IGF and IGFBP levels. RESULTS Adipose tissue cultures secreted more IGF-II than IGF-I protein (1.14±0.41 vs. 0.26±0.09 μg/l [mean±SEM]; P<0.02). IGF-I mRNA and protein levels were stimulated by GH (to 340% [153; 477] (median [interquartiles]) and 270±26%, respectively; P<0.003), and inhibited by IL-1β (to 28% [21; 77] and 68±11%, respectively; P<0.003). TNF-α reduced IGF-I and IGF-II protein levels to 51±8% and 69±8%, respectively (P≤0.002), without affecting mRNA levels. IGF protein levels were unaffected by DXM, insulin and IL-6. All IGFBPs IGFBP-1 were expressed. IGFBP-4 was by far the most predominant IGFBP by immunoassay and WLB revealed two bands at 28 and 24 kDa, most likely representing glycosylated and non-glycosylated IGFBP-4. CONCLUSION Adipose tissue cultures secrete more IGF-II than IGF-I, and predominantly IGFBP-4. The secretion of IGF-I is affected by GH, IL-1β and TNF-α, whereas IGF-II is affected by TNF-α only. Hence, cytokines may control adipocyte homeostasis by affecting local IGF-generation.
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Affiliation(s)
- Mette Faurholdt Gude
- The Medical Research Laboratories, Institute of Clinical Medicine & Department of Endocrinology and Internal Medicine, Nørrebrogade, Aarhus University Hospital, DK-8000 Aarhus C, Denmark
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Iiritano S, Chiefari E, Ventura V, Arcidiacono B, Possidente K, Nocera A, Nevolo MT, Fedele M, Greco A, Greco M, Brunetti G, Fusco A, Foti D, Brunetti A. The HMGA1-IGF-I/IGFBP system: a novel pathway for modulating glucose uptake. Mol Endocrinol 2012; 26:1578-89. [PMID: 22745191 DOI: 10.1210/me.2011-1379] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We previously showed that loss of the high mobility group A1 (HMGA1) protein expression, induced in mice by disrupting the Hmga1 gene, considerably decreased insulin receptor expression in the major target tissues of insulin action, causing a type 2-like diabetic phenotype, in which, however, glucose intolerance was paradoxically associated with increased peripheral insulin sensitivity. Insulin hypersensitivity despite impairment of insulin action supports the existence of molecular adaptation mechanisms promoting glucose disposal via insulin-independent processes. Herein, we provide support for these compensatory pathways/circuits of glucose uptake in vivo, the activation of which under certain adverse metabolic conditions may protect against hyperglycemia. Using chromatin immunoprecipitation combined with protein-protein interaction studies of nuclear proteins in vivo, and transient transcription assays in living cells, we show that HMGA1 is required for gene activation of the IGF-binding proteins 1 (IGFBP1) and 3 (IGFBP3), two major members of the IGF-binding protein superfamily. Furthermore, by using positron emission tomography with (18)F-labeled 2-fluoro-2-deoxy-d-glucose, in combination with the euglycemic clamp with IGF-I, we demonstrated that IGF-I's bioactivity was increased in Hmga1-knockout mice, in which both skeletal muscle Glut4 protein expression and glucose uptake were enhanced compared with wild-type littermates. We propose that, by affecting the expression of both IGFBP protein species, HMGA1 can serve as a modulator of IGF-I activity, thus representing an important novel mediator of glucose disposal.
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Affiliation(s)
- Stefania Iiritano
- Dipartimento di Scienze della Salute, Università di Catanzaro Magna Græcia, 88100 Catanzaro, Italy
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Salazar-Ortiz J, Camous S, Briant C, Lardic L, Chesneau D, Guillaume D. Effects of nutritional cues on the duration of the winter anovulatory phase and on associated hormone levels in adult female Welsh pony horses (Equus caballus). Reprod Biol Endocrinol 2011; 9:130. [PMID: 21958120 PMCID: PMC3195710 DOI: 10.1186/1477-7827-9-130] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 09/29/2011] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Mares have an annual reproductive rhythm, with a phase of inactivity in midwinter. The aim of this study was to determine the impact of food restriction on physiological and metabolic hallmarks of this rhythm. METHODS Over three successive years, 3 groups of 10 mares were kept under natural photoperiod. A 'well-fed' group was fed to maintain the mares in good body condition; a 'restricted' group received a diet calculated to keep the mares thin and a 'variable' group was fed during some periods like the 'restricted' group and during some other periods like the 'well-fed' group, with the aim of mimicking the natural seasonal variation of pasture availability, but a few months in advance of this natural rhythm. RESULTS Winter ovarian inactivity always occurred and was long in the restricted group. In contrast, in the 'well-fed' group, 40% of mares showed this inactivity, which was shorter than in the other groups. Re-feeding the 'variable' group in autumn and winter did not advance the first ovulation in spring, compared with the 'restricted' group. Measurements of glucose and insulin concentrations in mares from the 'restricted' group during two 24 h periods of blood sampling, revealed no post-prandial peaks. For GH (Growth hormone), IGF-1 and leptin levels, large differences were found between the 'well-fed' group and the other groups. The glucose, insulin, GH and leptin levels but not melatonin level are highly correlated with the duration of ovulatory activity. CONCLUSIONS The annual rhythm driven by melatonin secretion is only responsible for the timing of the breeding season. The occurrence and length of winter ovarian inactivity is defined by metabolic hormones.
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Affiliation(s)
- Juan Salazar-Ortiz
- INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- CNRS, UMR6175 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- Université François Rabelais de Tours, F-37041 Tours, France
- IFCE, F-37380 Nouzilly, France
| | - Sylvaine Camous
- INRA, UMR1198 Biologie du Développement et Reproduction, F-78352 Jouy-en-Josas, France
- ENVA, F-94704 Maisons Alfort, France
| | - Christine Briant
- INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- CNRS, UMR6175 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- Université François Rabelais de Tours, F-37041 Tours, France
- IFCE, F-37380 Nouzilly, France
| | - Lionel Lardic
- INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- CNRS, UMR6175 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- Université François Rabelais de Tours, F-37041 Tours, France
- IFCE, F-37380 Nouzilly, France
| | - Didier Chesneau
- INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- CNRS, UMR6175 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- Université François Rabelais de Tours, F-37041 Tours, France
- IFCE, F-37380 Nouzilly, France
| | - Daniel Guillaume
- INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- CNRS, UMR6175 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France
- Université François Rabelais de Tours, F-37041 Tours, France
- IFCE, F-37380 Nouzilly, France
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Bielohuby M, Sawitzky M, Stoehr BJM, Stock P, Menhofer D, Ebensing S, Bjerre M, Frystyk J, Binder G, Strasburger C, Wu Z, Christ B, Hoeflich A, Bidlingmaier M. Lack of dietary carbohydrates induces hepatic growth hormone (GH) resistance in rats. Endocrinology 2011; 152:1948-60. [PMID: 21427215 DOI: 10.1210/en.2010-1423] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
GH is a well established regulator of growth, lipid, and glucose metabolism and therefore important for fuel utilization. However, little is known about the effects of macronutrients on the GH/IGF system. We used low-carbohydrate/high-fat diets (LC-HFD) as a model to study the impact of fat, protein, and carbohydrates on the GH/IGF-axis; 12-wk-old Wistar rats were fed either regular chow, a moderate, protein-matched LC-HFD, or a ketogenic LC-HFD (percentage of fat/protein/carbohydrates: chow, 16.7/19/64.3; LC-HF-1, 78.7/19.1/2.2; LC-HF-2, 92.8/5.5/1.7). After 4 wk, body and tibia length, lean body mass, and fat pad weights were measured. Furthermore, we investigated the effects of LC-HFD on 1) secretion of GH and GH-dependent factors, 2) expression and signaling of components of the GH/IGF system in liver and muscle, and 3) hypothalamic and pituitary regulation of GH release. Serum concentrations of IGF-I, IGF binding protein-1, and IGF binding protein-3 were lower with LC-HF-1 and LC-HF-2 (P < 0.01). Both LC-HFD-reduced hepatic GH receptor mRNA and protein expression, decreased basal levels of total and phosphorylated Janus kinase/signal transducers and activators of transcription signaling proteins and reduced hepatic IGF-I gene expression. Hypothalamic somatostatin expression was reduced only with LC-HF-1, leading to increased pituitary GH secretion, higher IGF-I gene expression, and activation of IGF-dependent signaling pathways in skeletal muscle. In contrast, despite severely reduced IGF-I concentrations, GH secretion did not increase with LC-HF-2 diet. In conclusion, lack of carbohydrates in LC-HFD induces hepatic GH resistance. Furthermore, central feedback mechanisms of the GH/IGF system are impaired with extreme, ketogenic LC-HFD.
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Affiliation(s)
- Maximilian Bielohuby
- Endocrine Research Unit, Medizinische Klinik-Innenstadt, Ludwig-Maximilians University, Munich, Germany
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Abstract
Polycystic ovary syndrome (PCOS) is characterised by anovulation, hyperandrogenism, and polycystic ovaries. Fifty percent of patients fulfil the criteria for the metabolic syndrome. The pathogenesis of PCOS may be looked as a vicious cycle involving hyperandrogenemia, central obesity, and insulin resistance and medical treatment should aim at breaking this cycle. Lifestyle intervention, oral contraceptives, and insulin sensitises such as metformin are the most commonly used treatment modalities. The thiazolidinediones rosiglitazone and pioglitazone were recently applied as insulin sensitising treatment in patients with PCOS. Thiazolidinediones activate the transcription of genes that affect glucose and lipid metabolism mediating decreased free fatty acid levels and decreased visceral fat mass. In the present article, we give an overview of the diverse effects of glitazone treatment in patients with PCOS. We review the studies comparing glitazone versus metformin and oral contraceptive treatment and recommend which patients should be treated with glitazones in daily praxis.
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Affiliation(s)
- Dorte Glintborg
- Department of Endocrinology and Metabolism, Odense University Hospital, Odense C, Denmark.
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Jeyaratnaganthan N, Grønbaek H, Holland-Fischer P, Espelund U, Chen JW, Flyvbjerg A, Vilstrup H, Frystyk J. Ascites from patients with alcoholic liver cirrhosis contains higher IGF-I bioactivity than serum. Clin Endocrinol (Oxf) 2010; 72:625-32. [PMID: 19769623 DOI: 10.1111/j.1365-2265.2009.03707.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Patients with liver cirrhosis have diminished hepatic IGF-I generation, resulting in low circulating levels, whereas data on IGF-I in ascites are sparse. Therefore, we compared the IGF-system in serum and ascites from cirrhotic patients. DESIGN AND PATIENTS The study comprised 43 patients (12 females) with ascites and liver function of 58 +/- 10% of normal. Serum and ascites were collected concomitantly in the fasting state. In 11 patients, second serum and ascitic samples were collected within the first week. Eleven matched controls were also included. All samples were assayed for IGF-related parameters by immunoassays and by cell-based IGF-I bioassay. RESULTS As compared with controls, serum total IGF-I, total IGF-II, pro-IGF-II and bioactive IGF-I were reduced in liver patients, whereas IGF-binding protein 1 (IGFBP-1), IGFBP-2 and the soluble IGF-II receptor were elevated (P < 0.005 for all). In ascites, all IGF-related peptides but pro-IGF-II were further reduced as compared with serum (P < 0.001). By contrast, bioactive IGF-I was fourfold elevated in ascites as compared with serum (2.20 +/- 0.33 vs. 0.55 +/- 0.08 microg/l, P < 0.001). In ascites, the IGF-I bioactivity signal was completely blocked by addition of IGFBP-3. Repetitive measurements (n = 11) in ascites showed that all peptides but IGFBP-1 remained unchanged within 1 week. CONCLUSIONS It is a novel observation that the in vitro bioactivity of IGF-I can be higher in fluids from an extravascular compartment than in serum, in contrast to immunoreactive levels. This supports different roles for endocrine and paracrine/autocrine IGF-I, but the pathophysiological significance of our observation remains to be clarified.
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Affiliation(s)
- Nilani Jeyaratnaganthan
- The Medical Research Laboratories, Clinical Institute, and Medical Department M (Diabetes & Endocrinology), Aarhus University Hospital, DK-8000 Aarhus C, Denmark
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Glintborg D, Støving RK, Hagen C, Hermann AP, Frystyk J, Veldhuis JD, Flyvbjerg A, Andersen M. Pioglitazone treatment increases spontaneous growth hormone (GH) secretion and stimulated GH levels in polycystic ovary syndrome. J Clin Endocrinol Metab 2005; 90:5605-12. [PMID: 16076946 DOI: 10.1210/jc.2005-0615] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Low GH levels, probably due to insulin resistance and increased abdominal fat mass, are well described in polycystic ovary syndrome (PCOS). GH acts as an important ovarian cogonadotropin, and GH disturbances may be an additional pathogenic factor in PCOS. Decreased abdominal fat mass and improved insulin sensitivity during pioglitazone treatment may affect GH secretion. OBJECTIVE The objective of the study was to investigate the effect of pioglitazone on GH levels in PCOS. DESIGN Thirty insulin-resistant PCOS patients were randomized to either 16 wk pioglitazone (30 mg/d) or placebo treatment. Before and after intervention, levels of fasting insulin, GH, total IGF-I, free IGF-I, IGF binding protein-1, IGF-II, free fatty acids, testosterone, and SHBG were measured. Patients underwent whole-body dual x-ray absorptiometry scans, pyridostigmine-GHRH tests, and 24-h 20-min integrated blood sampling for measurement of GH. RESULTS Peak GH and area under the curve for GH in pyridostigmine-GHRH tests and 24-h mean GH concentrations and pulsatile GH secretion significantly increased after pioglitazone treatment. No significant changes were observed in GH pulse frequency, pulse duration, approximate entropy levels, or basal GH release. Levels of IGF binding protein-1 significantly increased, whereas no significant differences were measured in total IGF-I and free IGF-I. Pioglitazone treatment significantly decreased fasting insulin and homeostasis model assessment levels. No significant changes were observed in Ferriman Gallwey score or androgen levels. CONCLUSION Pioglitazone treatment significantly increased GHRH-stimulated GH levels and 24-h pulsatile GH secretion, probably directly or indirectly due to improved insulin sensitivity.
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Affiliation(s)
- Dorte Glintborg
- Department of Endocrinology and Metabolism, Odense University Hospital, Denmark.
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Cingel-Ristić V, Schrijvers BF, van Vliet AK, Rasch R, Han VKM, Drop SLS, Flyvbjerg A. Kidney growth in normal and diabetic mice is not affected by human insulin-like growth factor binding protein-1 administration. Exp Biol Med (Maywood) 2005; 230:135-43. [PMID: 15673562 DOI: 10.1177/153537020523000208] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Insulin-like growth factor I (IGF-I) accumulates in the kidney following the onset of diabetes, initiating diabetic renal hypertrophy. Increased renal IGF-I protein content, which is not reflected in messenger RNA (mRNA) levels, suggests that renal IGF-I accumulation is due to sequestration of circulating IGF-I rather than to local synthesis. It has been suggested that IGF-I is trapped in the kidney by IGF binding protein 1 (IGFBP-1). We administered purified human IGFBP-1 (hIGFBP-1) to nondiabetic and diabetic mice as three daily sc injections for 14 days, starting 6 days after induction of streptozotocin diabetes when the animals were overtly diabetic. Markers of early diabetic renal changes (i.e., increased kidney weight, glomerular volume, and albuminuria) coincided with accumulation of renal cortical IGF-I despite decreased mRNA levels in 20-day diabetic mice. Human IGFBP-1 administration had no effect on increased kidney weight or albuminuria in early diabetes, although it abolished renal cortical IGF-I accumulation and glomerular hypertrophy in diabetic mice. Increased IGF-I levels in kidneys of normal mice receiving hIGFBP-1 were not reflected on kidney parameters. IGFBP-1 administration in diabetic mice had only minor effects on diabetic renal changes. Accordingly, these results did not support the hypothesis that IGFBP-1 plays a major role in early renal changes in diabetes.
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Affiliation(s)
- Vesna Cingel-Ristić
- Laboratory of Pediatrics, Subdivision of Molecular Endocrinology, Room Ee1500, Erasmus MC, PO.Box 1738, 3000 DR Rotterdam, The Netherlands.
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